The present invention relates to an electronic device comprising a module which includes an antenna and an RFID chip electrically connected to the antenna.
Among the applications of an electronic device which comprises an RFID chip electrically connected to an antenna (hereinafter referred to as a module), there is a rubber product in which an electronic device comprising a module is embedded. Such conventional technology is disclosed in reference 1, Japanese Patent Unexamined Publication No. JP2002-272589A.
The above-mentioned Reference 1 describes a method in which a through-hole is formed in a corner at the edge of a mat, that is, a rubber product, a module is inserted in the through-hole,
unvulcanized rubber is also inserted in the through-hole to enclose the module, and pressure and heat are applied from both sides of the unvulcanized rubber to vulcanize it, thereby making it a unified part of the vulcanized rubber that makes up the mat.
An IC card is a type of electronic device. Conventional technology relating to an IC card is disclosed in reference 2, Japanese Patent Unexamined Publication No. JP11-345299A.
The above-mentioned Reference 2 describes a method to make a module movable. In this method, a module coated beforehand with a surface lubricant, such as a silicone oil, is disposed between a pair of base parts, and a resin is then filled in and cured between the pair of base parts.
In the method which employs conventional technology to make a module movable, a module coated with a surface lubricant is enclosed by a resin (to be cured). Using this technique, even though the module does not come into direct contact with the resin, it is movable only within the limited space surrounded by the cured resin, so that the resultant effect of stress dispersion is very small.
In addition, the conventional technology, there are possibilities of causing bonding fracture between an RFID chip and an antenna, as well as antenna deformation. Also, there are cases in which, in mounting an electronic device to a rubber product, a module is embedded in vulcanized rubber by vulcanizing unvulcanized rubber, with priority being placed on the appearance or design or a need to satisfy the function requirements of the rubber product.
Usually, a process of vulcanizing unvulcanized rubber involves heating the unvulcanized rubber to a temperature of 100° C. to 300° C. and then cooling the heated rubber down to room temperature. The process causes the rubber to largely shrink, because the linear thermal expansion coefficient of rubber is very large. Therefore, the vulcanization process tends to cause a bonding fracture between an RFID chip and an antenna, as well as antenna deformation.